1. Field of the Invention
The present invention relates to plastic panels (or slabs) and particularly to such items for use as production boards and/or pallets and the like. Even more particularly the invention relates to production boards or pallets useful in the production of unitary concrete masonry products such as paving stones and the like.
2. The Prior Art Background
Concrete masonry units such as paving stones and the like are produced in manufacturing facilities where the paving stones are cast and cured and eventually stored. The production operations include, inter alia, molding, compacting, vibrating, heating in high humidity, washing, brushing, cleaning, stacking, etc. Traditionally the stones are carried on a production pallet during the various production operations. Such pallets are thus exposed to the same set of conditions as the stones undergoing production. In addition, the pallets are subject to additional wear and tear because they must be handled by automated devices such as stackers conveyors and/or by human operated machines such as fork lifts. Finally after the concrete products are unloaded the pallets must be cleaned and stacked for reuse. Prior art patents describing the production of paving stones and the like include U.S. Pat. No. 6,142,713 to Woolford, et al., U.S. Pat. No. 7,048,472 to Woolford, et al. and U.S. Pat. No. 5,568,994 to Dawson.
In the past there have been a variety of types of boards and/or pallets used in the concrete products industry. For example, useable prior art boards have been fabricated from materials such as hard wood, steel, and synthetic thermoplastic materials. Pallets fabricated from hard wood or thermoplastic materials often require internal or external strengthening. Prior art pallets and boards have also been fabricated as composite structures including a wooden or plastic laminated core covered by a plastic outer layer.
Commercially it has been known that useful pallets and/or boards should be lightweight, sturdy, long-lasting, damage and wear resistant, dimensionally stable and rigid. In addition it has been known that such products sometimes wear out so as to no longer be useful. Therefore it is desirable for the same to be fabricated from recyclable materials such as synthetic thermoplastic materials. Accordingly it is well known that molded plastic panels may be used as production pallets in the concrete masonry unit.
Although it is well known to use molded plastic panels as production pallets in the concrete masonry unit industry, such use has not been without its shortcomings. Dimensional stability is highly desirable and yet it is difficult to fabricate a panel from a thermoplastic material without substantial warping and/or difficulty in filling the mold. Furthermore, where internal steel strengthening bars are utilized to provide strength and rigidity to the plastic panel, the reclamation of the thermoplastic material from worn out panels is hindered. To solve such problems, it is known to mold the panel as two separate halves to enhance the molding procedure. Such halves are then joined together so as to present a single panel. Additional labor and hardware or bonding agents or heat have been necessary in the past to join the halves and keep them from later parting and causing difficulties somewhere along their journey.
In sum, the concrete masonry unit industry in particular is continually in need of better and more commercially beneficial equipment to enhance, improve and facilitate the overall production process. In particular the concrete masonry unit industry is continually in need of improved, enhanced and less expensive equipment such as production boards and the like.